In the galvanic deposition or electroplating of cathodes with metal from an anode, the anode and the cathode are immersed in an electrolyte forming an electroplating bath and connected to a source of electric current, usually direct current, polsed so that the metal of the anode solubilizes in the bath and by ionic transport ultimately is deposited upon the cathode.
In high capacity cyanide baths for copper plating, for example, the anodes are generally solid bodies supported by angles and juxtaposed with the cathode. For acid baths solid anodes of phosphor copper may be used.
Electroplating of copper can be utilized to deposit protective coatings or conductive or decorative coatings, to form shapes of copper metal which are difficult to fabricate in other ways, and for a variety of purposes. For example, the coating may have to be applied to intricate shapes, e.g. to printing drums or to printed circuit boards or to other electronic and electrical devices.
In this case, to ensure a uniform deposition of the plated metal upon the cathode, auxiliary electrodes may be provided which can consist of electrode holders, e.g. titanium baskets, containing pieces of the anode metal, i.e. anode bodies. Such electrodes may also be used as the principal electrodes in many cases. With such auxiliary or main electrodes, it is important that the anode metal be solubilized substantially uniformly from the anode bodies, the uniformity of solubilization being related to the uniformity of plating and the operating effectiveness of the bath. This has been found to be particularly important for precision electronic equipment and high-cost items.
The current technique involves the use of copper granules, electrolytic copper scrap and like materials as anode bodies.
However, with the existing systems, significant difficulties have been encountered. For example, with anode bodies of the irregular shapes hitherto employed, the filling of the baskets to a fixed or constant packing density has been difficult so that the quantity of anode metal per unit volume in the basket, for example, fluctuated during the course of a plating process.
The contact surfaces between the granules varied significantly and hence the available surface, i.e. the surface at which solubilization of the metal occurred, fluctuated substantially.
Attempts were made to overcome these disadvantages.
For example, it has been proposed to use wire sections which have the advantage that they are all of a uniform character if of the same diameter and length. However, the aforementioned problems cast a shadow upon this technique and, in addition, the wire sections tended to bridge across the filling cross section and prevent further packing of the baskets.
In general, therefore, the use of baskets with anode bodies heretofore has been plagued by a variety of problems which have necessitated almost daily removal of the baskets and hence interruption of the plating operation for servicing. This of course cuts production and wastes energy since the baths generally have to be reheated. The downtime can be several hours in each case.